Extrusion die



Feb. 15, 1944." A, M. WEBB 2,341,749

' EXTRUSION DIE Filed March 14, 1942 2 Sheets-Sheet 1 IN VEN TOR.

Feb. 15, 1944. B 7 2,341,749

EXTRUS ION DIE Filed March 14, 1942 2 Sheets-Sheet 2 i l C --ZLZ- I l l I 2/ A 2/ V w INVENTOR.

, ay K Patented Feb. 15, 1944 iiNi'l'ED STATES PATENT UFFICE ax'rmisIoN ma Arthur M. Webb, Los Angeles, Calif. Application March 14, 1942. Serial No. 434,766 '5 Claims. .(Cl. 207-171 My invention pertains to the extrusion art, and more particularly to extrusion dies and the processes involved in the complete press cycle.

One of the objects of my invention is to eflect an increase in the extruding speed and to shorten the time period of the extrusion cycle.

Another object is to reduce the "working of the metal.

Another object is to increase the tensile strength of the extrusions.

Another object is to reduce the number of men required in the crew.

And a still additional object is to make it unnecessary to apply a caustic to the bearing after each extrusion.

The difficulties that have been encountered in the prior art, and the means by which the present invention overcomes them, can best be explained with reference to the accompanying drawings, in which-- Fig, 1 is a diagrammatic illustration of the extrusionequipment with the tools in place, and with the platen and cylinder block shown in section.

Fig. 2 is also a diagrammatic view, but shows the tool container and tools and the forward end of the run-out table moved to the extruding position.

Fig. 3 shows the tool container in the shear arbor, where the dummy block and the butt of the ingot are sheared from the'face of the die.

Fig. 4 is a face view of the various press tools," which are, reading from left to right: the locking plate, the tool container, adapter plate. back-up, and die-holder with the back-up in place,

Fig. 5 is a sectional view of the die, back-up, die holder, and locking key.

Fig. 6 is a plan view of an extrusion die of th type commonly used in the art.

Fig. '7 is a section through Fig. 6, and indicates the twisting of the extrusion.

Fig. 8 shows two views of a common extrusion form, and illustrates the direction of-- the twisting that characterizes the moulding before it has bee straightened.

Fig. 9 is a plan view of a form of die that embodies my new invention.

Fig. 10 is a sectional view of the die shown in Fig. 9, with the extrusion indicated as moving in a straight line from the bearing.

Fig. 11 is a plan view of another die embodying the same. features of my invention embodied in Figs. 9 and 10.

Fig. 12 is a front elevation of the die shown in Fig. 11.

Fig. 13 is a plan view 0! a die embodying a difterent feature of my invention.

Fig. 14 is a sectional view of the die oi Fig. 13, taken on line ll-ll of Fig. 13.

Fig. 15 is a sectional view taken on line |6l5 of Fig. 13.

Fig. 16 shows how the die shown in Figs. 13. i4 and 15 may be changed to include the features of die construction illustrated in Figs. 9. 10, 11 and 12. 1 g

It is well known in the extrusion art that the thicker sections of the extrusion take the longer to form. For example, the metal that passes through the wide portion 8 of the bearing I of Fig. 6, does not form as quickly as the metal passing through the narrow portion 2. It is therefore necessary that portion 3 be longer than portion 2, as shown in Fig. 7. It is not practical for the bearing to have a uniform length equal to the length required for the thickest section.

' because excessive bearing length for the thinner sections either results in injurious rubbing of the formed metal on the die steel, or in an accumulation of dirt or "was where the formed metal takes-off" the bearing. Such an accumulation builds up until it rubs against the metal and causes longitudinal grooves, called die lines. It is consequently highly desirable that "relief" be cut in the die where the effective length of the bearing ends. as indicated at t and b in Fig. 7. Because of this inequality in the length of time required to form sections of different thicknesses, the metal does not form on a straight line in the conventional type of die, but rather upon an irregular line corresponding to the effective end of the various portions of the bearing around its circumierence, the characteristics of this forming line being evident from the shape of the front end of the extrusion, as shown by the line 8-9 in Fig. 7. This uneven forming line causes the extrusion to bend, as indicated in the figure.

An extrusion having a cross section such as t in Fig. 8, invariably bends as indicated in the side view 'i, because there is more metal at the juncture of the two arms of the v and hence a longer effective bearing and a later forming position for this part of the moulding.

The twisted extrusion is initially straightened by forcibly guiding the front end for several feet. after which it is maintained in place by a heavy roll tachometer, indicated at I in Fig. 1. and then by the run-out table II itself. When the extrusion has been heat treated, bowing and twisting again occurs. apparently because'of diflerential strains in the metal that were set up during the forced removal of the original twists. While many of these final bows and twists are removed mechanically, others are removed by hand-an operation that requires tme and expense'.

One object of th present invention is the prevention of the initial twisting as the metal passes through the die. a corollary object being the elimination of the manual straightening operation.

I achieve these objects by forming the metal on a line perpendicular to the direction of the flow of the metal. The walls of the bearing, of course. must vary in length according to the thickness of the contiguous section of the moulding. as the preceding paragraphs have explained, but I reconcile these apparently conflicting requirements by what might be called an inverted bearing."

Figs. 9, 10, 11 and 12 illustrate dies constructed according to the inverted bearing principle.

The die in Figs. 9 and 10 is designed to extrude a moulding identical to that for which the standard type die of Figs. 6 and 7 is intended. It will be noted, however, that the extra length of the bearing for the thicker section has been added to the forward end-that is, to the face of the die. The back ends of portions 2 and 3 are on a line transvers to the direction of flow of the metal, andiconsequently lie in a plane that lies transverse to the walls of the bearing. The extrusion I! from a die constructed in this manner, will move in a straight line.

The die illustrated in Figs. 11 and 12 is intended for an extrusion having a cross section substantially like that shown in view 6 of Fig. 8, and is intended to prevent the twisting indicated in view 1 of Fig. 8. Inasmuch as the thickest portion of this moulding is at the angular juncture of the two arms, the part of the bearing that forms this portion must be longer than the other portions of the bearing, as indicated at It in Fig. 12. Corresponding sections of the symmetrical arms I have corresponding dimensions, and the corresponding walls ii of the bearing are consequently of uniform length. but shorter than the walls that form the thicker section of the hearing. The walls of the relief portion it are of uniform length, because the back walls of the" bearing terminate in a plane that is transverse to the direction of flow of the metal.

Other objects of the present invention are to increase the extrusion speed and to produce extrusions of greater tensile strength. The maximum speed with which the metalmay be extruded, is determined by the speed at which "broken surface" occurs. The surface of an extruding section has a frictional force exerted upon it by the bearing, and consequently there is a greater tension in the surface portion than there is near the center. When the surface tension exceeds the tensile strength of the metal at the particular temperature at which it is being extruded, the critical point is reached- Beyond this point, broken surface is produced if either the temperature or pressure is increased. or if the speed is accelerated.

Another factor that determines the point at which broken surface occurs, is the amount of "working" the metal experiences before it enters the bearing. Other things being equal, the more working the grains have received, the slower the speed at which the metal must be extruded if broken surface is to be avoided.

The present invention aims to increase the extruding speed by reducing the working of the metal. The heated ingot, under the pressure of the hydraulic ram. is in a semi-plastic state as it flows into the bearing, and it has been found that broken surface is most likely to occur in those sections of the moulding that are formed by the portions of the bearing into which it is the most dimcult for the metal to flow. I therefore reduce the working of the metal in the ingot by directing and equahzing the flow as much as possible by a suitable lead-in" port between the face of the die and the bearing. This phase of my invention is illustrated by Figs. 13, 14 and 15. Fig. 14 being a cross-section through the portion of the die that forms the thinner part of the extrusion, and Fig. 15 a section through the part of the die that forms the thicker section. It will be noted that th walls It and 20 for the lead-in to the wider part of the bearing, are arranged to direct the inflow of a greater amount of metal than walls I! and ll of the lead-in for the narrower part of the bearing.

Other objects of my invention, achieved through balancing the flow, are a further reduction in the time of the extrusion cycle and the elimination of the application of a caustic to the rear portion of the bearing after each piece of moulding has been extruded, and the reduction of the press crew by one man.

As may be inferred from the fact that the extruding speed must be lessened the more the metal is worked, the working of the metal results in an increase of plasticity for a given temperature and pressure. It therefore takes longer to form. As soon as the metal is formed, the pressure is released, and the friction of the hearing a ainst the extrusion is then reduced to a small fraction of its former value. The metal then takes off from the bearing. When this occurs before the end of the bearing is reached, a wash develops ln the manner previously described.

. solution. There are several disadvantages to this.

It consumes time, contributes to the formation of another wash by chemical reaction; and if emery cloth is used, it wears ofl the rear of the bearing, producing what is known as a "hill-top bearing.

By providing a suitable lead-in orifice between the face of the die and the bearing, the metal is worked uniformly so that the forming all takes place in the same plane at the rear end of the bearing. thus avoiding the production of wash.

The elimination of the caustic applying operation, reduces the time period of the extrusion cycle and makes it possible to rearrange the duties of the crew so that it may be reduced from four to three men.

Fig. 18 illustrates the method of adding a. lead-l in orifice to a die having an inverted bearing. Views A and -B correspond to the sections taken on lines ll-lt and lS-Il of Fig. 13, but show how these sections appear when both an inverted bearing and a lead-in orifice are used. Reference line 2| shows that the posterior walls of the bearing all terminate in the same plane, a condition that does not prevail in Figs. 14 and 15, where the bearing is not inverted, as will be seen by referring to lines 22 and 23, which are in line on the two figures. Line 24, Fig. 16, indicates the position of the anterior end of the bearing .25 for the narrow section of the extrusion, and it will be noted that the extra, length of bearing 26 for the thicker portion of the extrusion extends beyond line 24, accordin to the inverted bearing requirements. The lead-in walls l'l', l8, l9, and 20 correspond to walls l1, l8, l9 and 20 of Figs. 14 and 15.

When the inverted bearing is used without a lead-in opening the irregular face of the die makes it necessary to make certain changes in the method of handling the extrusions and the equipment. The butt of the ingot 21, Fig. 3, always sticks to the face of the die 28 regardless of the nature of its surface. The present practice is to move the run-out table II far enough back for the press tools 32 to enter a shear arbor 29 and for the face of the die 28 to aline with the shear 30, which is moved across the face of the die by hydraulic pressure. The dummy block 3| adheres to the butt, and they are then knocked apart.

When an inverted bearing is used without a lead-in, the uneven surface of the die makes this shearing operationimpractical. The extrusion should therefore be sheared off immediately behind the tool container on the run-out table. This can be done by placing ashear arbor saw, or other suitable cutter in this position, and oper- 'ating it by a lever actuated by the movement of the table itself as it moves back from the extruding or press position. After the run-out table has been moved far enough back for the tools 32 to clear the platen 33, a pair of mechanically operated tongs may be arranged to clamp the butt and dummy block automatically so thatthe further movement of the run-out table will cause the sheared extrusion to be pulled through the It is contemplated that those skilled in the art will make various changes from the structures and processes shown in the drawings and described in this specification. The prior art discloses dies that are not of integral construction, so that the bearing or relief portions, for example, may be replaced. This form of construction may, of course, be used for my improved dies.

Other additions, changes, modifications and omissions may be made without departing from the broad spirit of my invention as defined in the appended claims.

I claim:

1. An extrusion die having a bearing the wall of which terminates all around its posterior end in a plane perpendicular to said wall, the length of the wall varying around its peripher substantially directly as the Width of the portion of the bearing that it bounds.

2. An extrusion die for irregular shapes having a bearing with generally parallel sides, and an inlet for said bearing that tapers thereto from a relatively Wide opening at the face of the die,

' at least a portion of the wall of said inlet being die. This, of course, produces a somewhat longer butt, but that is of little consequence comp to the advantages gained.

In Figs. 1 and 2 the locking plate 3d, operated by hydraulic means, is shown in the platen 33. In Fig. 1 the locking plate is shown in its inoperative position, and in Fig. 2 it is pictured in its locking position behind the tool container 35 where it immobilizes the tools against the pressure of the cylinder block 36, which in operation is moved by hydraulic means into firm contact with the face of the die 28. The ram 31 then presses on the dummy block 3| and forces the metal of the ingot 21 through the die.

curved longitudinally, said opening varying in width at the face of the die substantially directly as the amount of metal required to fill the closest portion of the bearing.

3. An extrusion die having at least one opening therethrough comprising a bearing, an inlet, and a relief outlet, the junction of said outlet and bearing lying throughout its circumference in a plane perpendicular to the walls of the bearing, and certain portions of the juncture of said inlet and bearing being a, greater distance from said junction than are certain other portions of said juncture.

4. An extrusion die having a bearing with generally parallel sides, an inlet for said bearing that tapers thereto from a relatively wide opening at the face of the die, and a relief outlet for said bearing, the junction of said outlet and bearing lying throughout its circumference in a plane perpendicular to the walls of the bearing, and at least one part of the juncture of said inlet and bearing lying in a different plane than the balance of said juncture.

5. An extrusion die for irregular shapes comprising a bearing with generally parallel sides and an inlet for said bearing that tapers thereto from a relatively wide opening at the face of th die, the breadth of said opening varying at the face of the die substantially directly as the width of the cross-section of the bearing taken on a line in the same longitudinal plane as said breadth.

ARTHUR M. WEBB. 

